The long-term objectives are to define molecular mechanisms by which a specific translocation of chromosome 8 leads to apparent transcriptional activation of the cellular proto-oncogene c-myc in Burkitt's lymphoma (BL), an undifferentiated B-lymphocyte cancer of man. The mechanism of c-myc activation will be examined by (1)\molecular cloning and characterization of the Ramos BL c-myc alleles, (2)\characterization of the c-myc transcript; and (3)\transfection of molecular clones of c-myc into B-lymphoid cells to study the expression of the transferred c-myc genes. A recombinant DNA library will be constructed from Ramos DNA in bacteriophage vectors. Phage clones containing c-myc gene will be identified by in situ hybridization screening of plaques and purified. Cloned c-myc genes will be characterized by restriction enzyme mapping and DNA sequence analysis to identify key structural differences between the normal and rearranged alleles that might be related to their functional differences. The structure of the c-myc transcripts will be examined by Northern blotting and S1 nuclease mapping techniques. These studies will test the hypothesis that the effects of c-myc in Ramos BL is due to overexpression of a normal c-myc transcript (gene dosage model of malignancy). Finally, to detect the possible presence of a transcriptional enhancer sequence adjacent to the rearranged Ramos c-myc allele, the isolated c-myc alleles will be cloned into the shuttle vector pSV2-neo. These constructs will be transfected into NIH3T3 cells and B-lymphoblastoid cell lines to detect differences in expression between the normal and rearranged c-myc allele responsible for enhanced expression. Transfection studies might also reveal differences in the ability of fibroblasts versus lymphoid to several certain classes of activated proto-oncogenes. Although BL responds to chemotherapy, early clinical relapse after remission is often characterized by resistance to further therapy and a poor prognosis. Illumination of mechanisms of enhanced expression of c-myc in BL and its biological role in the genesis of this lymphoma might suggest whether this pathway is a potential target for experimental intervention. Results from these studies may be relevant to other proto-oncogenes structurally and functonally related to c-myc, and thus to other cancers in which aberrant expression of these genes might have a role in the genesis or maintenance of the malignant phenotype. (X)